An interventional guide wire or other interventional device is often used in medical procedures that attempt to establish a pathway through a heavily stenosed or chronically occluded vessel. A chronically occluded vessel is referred to as containing a chronic total occlusion CTO. During these procedures, the guide wire or device can only be of clinical benefit to establish vessel patency if it is advanced distally into the vessel true lumen.
At times during the process of advancing the guide wire or device through the stenosed vessel or CTO, and beyond the control of the operator, the guide wire or device may inadvertently enter into the wall of the vessel itself, i.e. the sub-intimal plane or space, or dissection plane. Once in this sub-intimal plane, it becomes difficult to navigate the guide wire or device through the sub-intimal tissue to re-gain access into the vessel true lumen at points distal to the occlusion, i.e., a “re-entry” into the vessel lumen from the sub-intimal space but around the CTO. The layer of tissue that separates the vessel true lumen from the sub-intimal plane is typically in the range from 100 to 500 micrometers for vessels in the diameter range from 2 mm to 4 mm, and from 100 to 3000 microns, in the largest vessels of the body.
There exist a variety of catheters for re-entry around a CTO. One is described and shown in U.S. Pat. No. 6,231,546. In the system of this US Patent, the re-entry catheter requires the operator to rotate a catheter shaft while observing a radiopaque marker on the catheter shaft to ensure that a side or lateral port is aimed at the true lumen of the blood vessel. Once the marker indicates the correct orientation of the lateral port, a cannula is extended through the lateral port in order to penetrate through the intimal layer of the blood vessel. It is believed that one drawback of this system is the requirement to rotate the catheter to the correct position while under fluoroscopic imaging otherwise an incorrect orientation of the cannula could cause internal hemorrhaging of the blood vessel.
Another system is described and illustrated in US Patent Application Publication 2013/0072957. In this publication, a balloon is used to orient the cannula into the proper orientation for re-entry into the true vessel lumen. To achieve this, the catheter utilizes an asymmetrical catheter lumen for the cannula. It is believed that this system also suffers from a similar drawback in that the lateral port of the cannula must be oriented in the correct direction towards the true lumen while under fluoroscopy. This is to ensure that the cannula does not penetrate away from the true lumen, which could lead to internal hemorrhaging.